Optical imaging system

ABSTRACT

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from an object side. At least two of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens include at least one inflection point. An object-side surface of the sixth lens is concave.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC 199(a) of Korean PatentApplication No. 10-2018-0002403 filed on Jan. 8, 2018 in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND 1. Field

This application relates to an optical imaging system including sixlenses.

2. Description of the Background

Small camera modules may be mounted in mobile communications terminals.For example, small camera modules may be mounted in thinned devices,such as mobile phones, or the like. Such a small camera module includesan optical imaging system including a small number of lenses so that itmay be made as thin as possible. For example, the optical imaging systemof the small camera module includes four or less lenses.

However, such an optical imaging system has a high f-number (F No.),such that it is difficult for the optical imaging system to be used in asmall camera module while still providing high performance.

The above information is provided as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

An optical imaging system includes a first lens, a second lens, a thirdlens, a fourth lens, a fifth lens, and a sixth lens sequentiallyarranged from an object side. At least two of the first lens, the secondlens, the third lens, the fourth lens, the fifth lens, and the sixthlens include at least one inflection point. An object-side surface ofthe sixth lens is concave.

One of an object-side surface and an image-side surface of the fourthlens may include an inflection point.

One of an object-side surface or an image-side surface of the fifth lensmay include an inflection point.

One of the object-side surface or an image-side surface of the sixthlens may include an inflection point.

The second lens may have a refractive index greater than a refractiveindex of the first lens, a refractive index of the third lens, arefractive index of the fourth lens, a refractive index of the fifthlens, and a refractive index of the sixth lens.

The fourth lens may have a refractive index less than a refractive indexof the second lens and greater than a refractive index of the firstlens, a refractive index of the third lens, a refractive index of thefifth lens, and a refractive index of the sixth lens.

The first lens may have positive refractive power.

The sixth lens may have negative refractive power.

An object-side surface of the fifth lens may be convex.

An f-number of the optical imaging system may be less than 2.

An optical imaging system includes a first lens, a second lens, a thirdlens, a fourth lens, a fifth lens, and a sixth lens sequentiallyarranged from an object side. One of an image-side surface of the firstlens and an image-side surface of the third lens is concave. One of anobject-side surface of the fourth lens and an image-side surface of thefourth lens includes an inflection point. One of an object-side surfaceof the fifth lens and an image-side surface of the fifth lens includesan inflection point. One of an object-side surface of the sixth lens andan image-side surface of the sixth lens includes an inflection point. V4is an Abbe number of the fourth lens, V5 is an Abbe number of the fifthlens, and V5-V4 is greater than 20 and less than 40.

The second lens may have a refractive index of 1.65 or higher.

The fourth lens may have a refractive index of 1.6 or higher.

OAL is a distance from an object-side surface of the first lens to animaging plane, FOV is a field of view of the optical imaging system, andOAL/FOV may be greater than 0.05 and less than 0.2.

An object-side surface of the fifth lens may be convex.

An object-side surface of the sixth lens may be concave.

An optical imaging system includes a first lens, a second lens, a thirdlens, a fourth lens, a fifth lens, and a sixth lens sequentiallyarranged from an object side. At least one of the fourth lens, the fifthlends, and the sixth lens includes at least one inflection point on bothan object-side surface and an image-side surface thereof. The secondlens has a refractive index that is higher than a refractive index ofeach of the first lens, the third lens, the fourth lens, the fifth lens,and the sixth lens.

At least two of the fourth lens, the fifth lends, and the sixth lens mayinclude at least one inflection point on both an object-side surface andan image-side surface thereof.

Each of the fourth lens, the fifth lends, and the sixth lens may includeat least one inflection point on both an object-side surface and animage-side surface thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating an example of an optical imaging system.

FIG. 2 illustrates graphs having curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 1.

FIG. 3 is a view illustrating an example of an optical imaging system.

FIG. 4 illustrates graphs having curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 3.

FIG. 5 is a view illustrating an example of an optical imaging system.

FIG. 6 illustrates graphs having curves representing aberrationcharacteristics of the optical imaging system illustrated in FIG. 5.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various lenses, members, components, or sections, theselenses, members, components, or sections are not to be limited by theseterms. Rather, these terms are only used to distinguish one member,component, region, layer, or section from another member, component,region, layer, or section.

Herein, it is noted that use of the term “may” with respect to anexample or embodiment, e.g., as to what an example or embodiment mayinclude or implement, means that at least one example or embodimentexists in which such a feature is included or implemented while allexamples and embodiments are not limited thereto.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

As described herein, a first lens refers to a lens closest to an object(or a subject), while a sixth lens refers to a lens closest to animaging plane (or an image sensor). In addition, all of radii ofcurvature and thicknesses of lenses, a distance from the object-sidesurface of the first lens to the imaging plane (OAL), an IMG HT (½ of adiagonal length of the imaging plane), and focal lengths are representedby millimeters (mm). Further, thicknesses of the lenses, gaps betweenthe lenses, and the OAL are distances measured based on optical axes ofthe lenses. Further, in a description for shapes of the lenses, themeaning that one surface of a lens is convex is that an optical axisportion of a corresponding surface is convex, and the meaning that onesurface of a lens is concave is that an optical axis portion of acorresponding surface is concave. Therefore, although it is describedthat one surface of a lens is convex, an edge portion of the lens may beconcave. Likewise, although it is described that one surface of a lensis concave, an edge portion of the lens may be convex.

An optical imaging system may include six lenses sequentially arrangedfrom an object side toward the imaging plane. For example, the opticalimaging system may include a first lens, a second lens, a third lens, afourth lens, a fifth lens, and a sixth lens that are sequentiallyarranged. The first to sixth lenses may be arranged with a predeterminedinterval therebetween. For example, a predetermined interval may beformed between an image-side surface of the first lens and anobject-side surface of the second lens.

The first lens may have refractive power. For example, the first lensmay have positive refractive power.

One surface of the first lens may be convex. For example, an object-sidesurface of the first lens may be convex. The first lens may have anaspherical surface. For example, both surfaces of the first lens may beaspherical. The first lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the first lensmay be formed of plastic. However, a material of the first lens is notlimited to plastic. For example, the first lens may be formed of glass.

The first lens may have a predetermined refractive index. For example,the refractive index of the first lens may be less than 1.6. The firstlens may have a predetermined Abbe number. For example, the Abbe numberof the first lens may be 50 or more.

The second lens may have refractive power. For example, the second lensmay have negative refractive power.

One surface of the second lens may be convex. For example, anobject-side surface of the second lens may be convex. The second lensmay have an aspherical surface. For example, both surfaces of the secondlens may be aspherical. The second lens may be formed of a materialhaving high light transmissivity and excellent workability. For example,the second lens may be formed of plastic. However, a material of thesecond lens is not limited to plastic. For example, the second lens maybe formed of glass.

The second lens may have a refractive index higher than those of one ormore of the other lenses of the optical imaging system. For example, therefractive index of the second lens may be 1.65 or more. The second lensmay have a predetermined Abbe number. For example, the Abbe number ofthe second lens may be less than 22.

The third lens may have refractive power. For example, the third lensmay have positive or negative refractive power.

One surface of the third lens may be convex. For example, an object-sidesurface of the third lens may be convex. The third lens may have anaspherical surface. For example, both surfaces of the third lens may beaspherical. The third lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the third lensmay be formed of plastic. However, a material of the third lens is notlimited to plastic. For example, the third lens may be formed of glass.

The third lens may have a refractive index that is relatively similar tothat of the first lens. For example, the refractive index of the thirdlens may be less than 1.6. The third lens may have an Abbe numbersimilar to that of the first lens. For example, the Abbe number of thethird lens may be 50 or more.

The fourth lens may have refractive power. For example, the fourth lensmay have positive or negative refractive power.

One surface of the fourth lens may be convex. For example, anobject-side surface of the fourth lens may be convex. The fourth lensmay have an aspherical surface. For example, both surfaces of the fourthlens may be aspherical. The fourth lens may have one or more inflectionpoints. For example, one or more inflection points may be formed on theobject-side surface or an image-side surface of the fourth lens.

The fourth lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the fourth lensmay be formed of plastic. However, a material of the fourth lens is notlimited to plastic. For example, the fourth lens may be formed of glass.

The fourth lens may have a refractive index lower than that of thesecond lens and higher than those of one or more of the other lenses ofthe optical imaging system. For example, the refractive index of thefourth lens may be 1.6 or more. The fourth lens may have an Abbe numberlower than that of the first lens. For example, the Abbe number of thefourth lens may be less than 30.

The fifth lens may have refractive power. For example, the fifth lensmay have positive refractive power.

One surface of the fifth lens may be convex. For example, an image-sidesurface of the fifth lens may be convex. The fifth lens may have anaspherical surface. For example, both surfaces of the fifth lens may beaspherical. The fifth lens may have one or more inflection points. Forexample, one or more inflection points may be formed on an object-sidesurface or the image-side surface of the fifth lens.

The fifth lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the fifth lensmay be formed of plastic. However, a material of the fifth lens is notlimited to plastic. For example, the fifth lens may be formed of glass.

The fifth lens may have a refractive index that is relatively similar tothat of the first lens. For example, the refractive index of the fifthlens may be less than 1.6. The fifth lens may have a predetermined Abbenumber. For example, the Abbe number of the fifth lens may be 50 ormore.

The sixth lens may have refractive power. For example, the sixth lensmay have negative refractive power.

One surface of the sixth lens may be concave. For example, anobject-side surface of the sixth lens may be concave. The sixth lens mayhave one or more inflection points. For example, one or more inflectionpoints may be formed on both surfaces of the sixth lens. The sixth lensmay have an aspherical surface. For example, both surfaces of the sixthlens may be aspherical.

The sixth lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the sixth lensmay be formed of plastic. However, a material of the sixth lens is notlimited to plastic. For example, the sixth lens may be formed of glass.

The sixth lens may have a refractive index that is relatively similar tothat of the first lens. For example, the refractive index of the sixthlens may be less than 1.6. The sixth lens may have a predetermined Abbenumber. For example, the Abbe number of the sixth lens may be 50 ormore.

The first to sixth lenses may have an aspherical shape, as describedabove. For example, at least one surface of all of the first to sixthlenses may be aspherical. Here, an aspherical surface of each lens maybe represented by the following Equation 1:

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {{Jr}^{20}.}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In equation 1, c is an inverse of a radius of curvature of the lens, kis a conic constant, r is a distance from a certain point on anaspherical surface of the lens to an optical axis, A to J are asphericalconstants, and Z (or SAG) is a distance between the certain point on theaspherical surface of the lens at the distance r and a tangential planemeeting the apex of the aspherical surface of the lens.

The optical imaging system may further include a stop. The stop may bedisposed between the first lens and the second lens.

The optical imaging system may further include a filter. The filter mayblock a partial wavelength from incident light incident through thefirst to sixth lenses. For example, the filter may block an infraredwavelength of the incident light.

The optical imaging system may further include an image sensor. Theimage sensor may provide the imaging plane on which light refracted bythe lenses may be imaged. For example, a surface of the image sensor mayform the imaging plane. The image sensor may be configured to implementa high level of resolution.

The optical imaging system may satisfy one or more of the followingConditional Expressions 1 to 4:

−0.7<f1/f2   Conditional Expression 1

20<V5−V4<40   Conditional Expression 2

0.05<OAL/FOV<0.5   Conditional Expression 3

0.2<Th6/Th5<0.9.   Conditional Expression 4

In addition, the optical imaging system may satisfy one or more of thefollowing Conditional Expressions 5 and 6:

0.05<OAL/FOV<0.07   Conditional Expression 5

0.2<Th6/Th5<0.06.   Conditional Expression 6

In the above Conditional Expressions 1-6, f1 is a focal length of thefirst lens, f2 is a focal length of the second lens, V4 is an Abbenumber of the fourth lens, V5 is an Abbe number of the fifth lens, OALis a distance from the object-side surface of the first lens to theimaging plane, FOV is a field of view of the optical imaging system, Th5is a thickness (in an optical axis portion) of the fifth lens, and Th6is a thickness (in an optical axis portion) of the sixth lens.

Next, optical imaging systems according to several examples will bedescribed.

First, an optical imaging system according to a first example will bedescribed with reference to FIG. 1.

The optical imaging system 100 in the first example may include aplurality of lenses having refractive power. For example, the opticalimaging system 100 may include a first lens 110, a second lens 120, athird lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens160.

The first lens 110 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The second lens 120 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The third lens 130 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The fourth lens 140 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fourth lens140. For example, the object-side surface of the fourth lens 140 may beconvex in a paraxial region and be concave in an area near the paraxialregion, and the image-side surface thereof may be concave in a paraxialregion and be convex in an area near the paraxial region.

The fifth lens 150 may have positive refractive power, and anobject-side surface thereof may be concave and an image-side surfacethereof may be convex. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fifth lens150.

The sixth lens 160 may have negative refractive power, and anobject-side surface thereof may be concave and an image-side surfacethereof may be concave. In addition, inflection points may be formed onboth surfaces of the sixth lens 160. For example, the object-sidesurface of the sixth lens 160 may be convex in a paraxial region and beconcave in an area near the paraxial region, and the image-side surfacethereof may be concave in a paraxial region and be convex in an areanear the paraxial region.

The second lens 120 and the fourth lens 140 may have relatively highrefractive indices. The second lens 120 may have the highest refractiveindex among the lenses in the optical imaging system 100, and the fourthlens 140 may have the second highest refractive index among the lensesin the optical imaging system 100. The refractive index of the secondlens 120 may be 1.66 or more, and the refractive index of the fourthlens 140 may be 1.6 or more. The first lens 110, the third lens 130, thefifth lens 150, and the sixth lens 160 may each have relatively lowrefractive indices. The refractive indices of the first lens 110, thethird lens 130, the fifth lens 150, and the sixth lens 160 may each be1.56 or less.

The second lens 120 and the fourth lens 140 may have relatively low Abbenumbers. The Abbe numbers of the second lens 120 and the fourth lens 140may each be 25 or less. The first lens 110, the third lens 130, thefifth lens 150, and the sixth lens 160 may each have relatively highAbbe numbers. The Abbe numbers of the first lens 110, the third lens130, the fifth lens 150, and the sixth lens 160 may each be 52 or more.

The optical imaging system 100 may include a stop ST. For example, thestop ST may be disposed between the first lens 110 and the second lens120. The stop ST may control an amount of light incident to an imagingplane 180.

The optical imaging system 100 may include a filter 170. For example,the filter 170 may be disposed between the sixth lens 160 and theimaging plane 180. The filter 170 may block an infrared ray incident tothe imaging plane 180.

The optical imaging system 100 may include an image sensor. The imagesensor may provide the imaging plane 180 on which light refractedthrough the lenses is imaged. The image sensor may convert an opticalsignal imaged on the imaging plane 180 into an electrical signal.

The optical imaging system 100 may have a low F No. The F No. of theoptical imaging system in the first example 100 may be 1.85.

The optical imaging system in the first example 100 may representaberration characteristics as illustrated in FIG. 2. Table 1 representscharacteristics of lenses of the optical imaging system in the firstexample 100, and Table 2 represents aspherical characteristics of theoptical imaging system in the first example 100.

TABLE 1 First Example f = 3.93 F No. = 1.85 FOV = 78.4 OAL = 4.600Radius of Thickness/ Refractive Abbe Focal Surface No. CurvatureDistance Index Number Length S1 First Lens 1.5228 0.6858 1.544 56.1003.297 S2 8.2704 0.0801 S3 Second Lens 14.4630 0.2200 1.660 20.350 −7.520S4 3.7084 0.3011 S5 Third Lens 15.0000 0.2946 1.544 56.100 −34.731 S68.3204 0.1420 S7 Fourth Lens 2.8245 0.2503 1.640 23.500 26.054 S8 3.27590.4152 S9 Fifth Lens −22.7673 0.5714 1.544 56.100 2.101 S10 −1.10300.2841 S11 Sixth Lens −1.6069 0.3300 1.544 56.100 −1.732 S12 2.46920.1345 S13 Filter Infinity 0.2100 1.517 64.200 S14 Infinity 0.6810 S15Imaging Plane infinity

TABLE 2 First Exemplary Embodiment S1 S2 S3 S4 S5 S6 S7 K −1.11493−23.70901 25.51264 6.69361 0.00000 0.00000 −28.60705 A 0.035445−0.084093 −0.121231 −0.065598 −0.099439 −0.262113 −0.228315 B 0.0298140.141397 0.299695 0.223732 0.133726 0.735503 0.266229 C −0.102629−0.272213 −0.622868 −0.501495 −0.597395 −2.360882 −0.453950 D 0.2848360.585064 1.790576 1.479639 1.212968 5.381433 0.607804 E −0.474983−0.998765 −4.046274 −3.464256 −2.223379 −8.728256 −0.664888 F 0.4540581.011072 5.475196 4.967442 3.274299 8.995004 0.473682 G −0.231752−0.543383 −3.913831 −3.824447 −3.169047 −5.271134 −0.212232 H 0.0463490.119779 1.148347 1.237336 1.333581 1.340995 0.047636 J 0 0 0 0 0 0 0First Exemplary Embodiment S8 S9 S10 S11 S12 K 17.83478 −64.15173−1.38611 −8.10335 −6.56149 A −0.199626 −0.047115 0.208547 −0.022827−0.133569 B 0.138156 0.077066 −0.231460 0.174659 0.066479 C −0.154481−0.282510 0.114064 0.186177 −0.027667 D 0.162165 0.400297 −0.007388−0.083562 0.008713 E −0.155989 −0.325101 −0.011143 0.020700 −0.002004 F0.099397 0.149132 0.003530 −0.002969 0.000304 G −0.031726 −0.034944−0.000369 0.000232 −0.000026 H 0.003895 0.003240 0.000010 −0.0000080.000001 J 0 0 0 0 0

A second example of an optical imaging system will be described withreference to FIG. 3.

The optical imaging system 200 in the second example may include aplurality of lenses having refractive power. For example, the opticalimaging system 200 may include a first lens 210, a second lens 220, athird lens 230, a fourth lens 240, a fifth lens 250, and a sixth lens260.

The first lens 210 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The second lens 220 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The third lens 230 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The fourth lens 240 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fourth lens240. For example, the object-side surface of the fourth lens 240 may beconvex in a paraxial region and be concave in an area near the paraxialregion, and the image-side surface thereof may be concave in a paraxialregion and be convex in an area near the paraxial region.

The fifth lens 250 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be convex. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fifth lens250.

The sixth lens 260 may have negative refractive power, and anobject-side surface thereof may be concave and an image-side surfacethereof may be concave. In addition, inflection points may be formed onboth surfaces of the sixth lens 260. For example, the object-sidesurface of the sixth lens 260 may be convex in a paraxial region and beconcave in an area near the paraxial region, and the image-side surfacethereof may be concave in a paraxial region and be convex in an areanear the paraxial region.

The second lens 220 and the fourth lens 240 may have relatively highrefractive indices. The second lens 220 may have the highest refractiveindex among the lenses in the optical imaging system 200, and the fourthlens 240 may have the second highest refractive index among the lensesin the optical imaging system 200. The refractive index of the secondlens 220 may be 1.66 or more, and the refractive index of the fourthlens 240 may be 1.6 or more. The first lens 210, the third lens 230, thefifth lens 250, and the sixth lens 260 may each have relatively lowrefractive indices. The refractive indices of the first lens 210, thethird lens 230, the fifth lens 250, and the sixth lens 260 may each be1.56 or less.

The second lens 220 and the fourth lens 240 may have relatively low Abbenumbers. The Abbe numbers of the second lens 220 and the fourth lens 240may each be 25 or less. The first lens 210, the third lens 230, thefifth lens 250, and the sixth lens 260 may each have relatively highAbbe numbers. The Abbe numbers of the first lens 210, the third lens230, the fifth lens 250, and the sixth lens 260 may each be 52 or more.

The optical imaging system 200 may include a stop ST. For example, thestop ST may be disposed between the first lens 210 and the second lens220. The stop ST may control an amount of light incident to an imagingplane 280.

The optical imaging system 200 may include a filter 270. For example,the filter 270 may be disposed between the sixth lens 260 and theimaging plane 280. The filter 270 may block an infrared ray incident tothe imaging plane 280.

The optical imaging system 200 may include an image sensor. The imagesensor may provide the imaging plane 280 on which light refractedthrough the lenses is imaged. The image sensor may convert an opticalsignal imaged on the imaging plane 280 into an electrical signal.

The optical imaging system 200 may have a low F No. The F No. of theoptical imaging system in the second example 200 may be 1.70.

The optical imaging system in the second example 200 may representaberration characteristics as illustrated in FIG. 4. Table 3 representscharacteristics of lenses of the optical imaging system 200, and Table 4represents aspherical characteristics of the optical imaging system inthe second example 200.

TABLE 3 Second Example f = 4.24 F No. = 1.70 FOV = 78.8 OAL = 4.896Radius of Thickness/ Refractive Abbe Focal Surface No. CurvatureDistance Index Number Length S1 First Lens 1.6600 0.6950 1.544 56.1004.098 S2 5.4642 0.0841 S3 Second Lens 6.5122 0.2200 1.660 20.350 −9.541S4 3.1791 0.2741 S5 Third Lens 4.4871 0.2980 1.544 56.100 43.466 S65.4023 0.3442 S7 Fourth Lens 3.3372 0.2500 1.640 23.500 −33.840 S82.8101 0.3775 S9 Fifth Lens 6.0280 0.5732 1.544 56.100 2.882 S10 −2.06050.5044 S11 Sixth Lens −2.1547 0.3400 1.535 55.700 −2.437 S12 3.51160.1000 S13 Filter Infinity 0.1100 1.517 64.200 S14 Infinity 0.7250 S15Imaging Plane infinity

TABLE 4 Second Exemplary Embodiment S1 S2 S3 S4 S5 S6 S7 K −1.25646−23.81437 23.93321 3.89759 0.00000 0.00000 −29.97367 A 0.031294−0.094924 −0.165237 −0.112865 −0.105932 −0.099682 −0.221376 B −0.0146280.163252 0.287358 0.369956 −0.091851 −0.120314 0.128916 C 0.126883−0.289000 −0.220232 −1.092286 1.329919 1.027016 0.190309 D −0.3611130.436251 −0.014969 2.990808 −5.491154 −3.071940 −0.778391 E 0.538167−0.534023 0.260344 −5.514483 11.217468 4.724795 1.102189 F −0.4461400.430597 −0.288769 6.091503 −12.601729 −4.078659 −0.819680 G 0.191263−0.189322 0.163725 −3.592907 7.404120 1.862348 0.309763 H −0.0335460.033293 −0.042062 0.872804 −1.767660 −0.345792 −0.046230 J 0 0 0 0 0 00 Second Exemplary Embodiment S8 S9 S10 S11 S12 K −19.77599 −72.14303−1.15918 −7.02665 −3.41770 A −0.243209 0.035310 0.125112 −0.094610−0.124420 B 0.223595 −0.083987 −0.105313 −0.010208 0.056137 C −0.2279660.089551 0.108087 0.040727 −0.022245 D 0.144192 −0.074910 −0.082446−0.018645 0.007512 E −0.038063 0.031505 0.035005 0.004229 −0.001938 F−0.006976 −0.006213 −0.008047 −0.000541 0.000344 G 0.006837 0.0004940.000948 0.000037 −0.000039 H −0.001183 −0.000006 −0.000045 −0.0000010.000002 J 0 0 0 0 −0.000001

A third example of an optical imaging system will be described withreference to FIG. 5.

The optical imaging system 300 in the third example may include aplurality of lenses having refractive power. For example, the opticalimaging system 300 may include a first lens 310, a second lens 320, athird lens 330, a fourth lens 340, a fifth lens 350, and a sixth lens360.

The first lens 310 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The second lens 320 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The third lens 330 may have negative refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave.

The fourth lens 340 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be concave. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fourth lens340. For example, the object-side surface of the fourth lens 340 may beconvex in a paraxial region and be concave in an area near the paraxialregion, and the image-side surface thereof may be concave in a paraxialregion and be convex in an area near the paraxial region.

The fifth lens 350 may have positive refractive power, and anobject-side surface thereof may be convex and an image-side surfacethereof may be convex. In addition, inflection points may be formed onthe object-side surface and the image-side surface of the fifth lens350.

The sixth lens 360 may have negative refractive power, and anobject-side surface thereof may be concave and an image-side surfacethereof may be concave. In addition, inflection points may be formed onboth surfaces of the sixth lens 360. For example, the object-sidesurface of the sixth lens 360 may be convex in a paraxial region and beconcave in an area near the paraxial region, and the image-side surfacethereof may be concave in a paraxial region and be convex in an areanear the paraxial region.

The second lens 320 and the fourth lens 340 may each have relativelyhigh refractive indices. The second lens 320 may have the highestrefractive index among the lenses in the optical imaging system 300, andthe fourth lens 340 may have the second highest refractive index amongthe lenses in the optical imaging system 300. The refractive index ofthe second lens 320 may be 1.66 or more, and the refractive index of thefourth lens 340 may be 1.6 or more. The first lens 310, the third lens330, the fifth lens 350, and the sixth lens 360 may each have relativelylow refractive indices. The refractive indices of the first lens 310,the third lens 330, the fifth lens 350, and the sixth lens 360 may eachbe 1.56 or less.

The second lens 320 and the fourth lens 340 may each have relatively lowAbbe numbers. The Abbe numbers of the second lens 320 and the fourthlens 340 may each be 25 or less. The first lens 310, the third lens 330,the fifth lens 350, and the sixth lens 360 may each have relatively highAbbe numbers. The Abbe numbers of the first lens 310, the third lens330, the fifth lens 350, and the sixth lens 360 may each be 52 or more.

The optical imaging system 300 may include a stop ST. For example, thestop ST may be disposed between the first lens 310 and the second lens320. The stop ST may control an amount of light incident to an imagingplane 380.

The optical imaging system 300 may include a filter 370. For example,the filter 370 may be disposed between the sixth lens 360 and theimaging plane 380. The filter 370 may block an infrared ray incident tothe imaging plane 380.

The optical imaging system 300 may include an image sensor. The imagesensor may provide the imaging plane 380 on which light refractedthrough the lenses is imaged. The image sensor may convert an opticalsignal imaged on the imaging plane 380 into an electrical signal.

The optical imaging system 300 may have a low F No. The F No. of theoptical imaging system in the third example 300 may be 1.85.

The optical imaging system in the third example 300 may representaberration characteristics as illustrated in FIG. 6. Table 5 representscharacteristics of lenses of the optical imaging system in the thirdexample 300, and Table 6 represents aspherical characteristics of theoptical imaging system in the third example 300.

TABLE 5 Third Example f = 3.93 F No = 1.85 FOV = 77.7 OAL = 4.651 Radiusof Thickness/ Refractive Abbe Focal Surface No. Curvature Distance IndexNumber Length S1 First Lens 1.5297 0.6936 1.544 56.100 3.423 S2 7.04400.0676 S3 Second Lens 6.1573 0.2200 1.660 20.350 −7.910 S4 2.8045 0.3440S5 Third Lens 15.2704 0.3263 1.544 56.100 −60.697 S6 10.3777 0.1906 S7Fourth Lens 2.7050 0.2643 1.640 23.500 43.832 S8 2.8830 0.3591 S9 FifthLens 136.3154 0.6051 1.544 56.100 2.018 S10 −1.1101 0.2560 S11 SixthLens −1.5960 0.3300 1.535 55.700 −1.690 S12 2.2531 0.1307 S13 FilterInfinity 0.2100 1.517 64.200 S14 Infinity 0.6540 S15 Imaging Planeinfinity

TABLE 6 Third Exemplary Embodiment S1 S2 S3 S4 S5 S6 S7 K −1.12419−23.70901 25.51264 4.39371 0.00000 0.00000 −28.60705 A 0.035045−0.145295 −0.224396 −0.114403 −0.128596 −0.223970 −0.125361 B 0.0314090.282947 0.453658 0.273763 0.259451 0.478023 0.063239 C −0.107096−0.376518 −0.509320 −0.176649 −1.405765 −1.381746 0.028484 D 0.2825410.376412 0.414946 −0.456830 4.443413 2.718434 −0.250774 E −0.447318−0.362563 −0.460090 1.721506 −9.267030 −3.755079 0.393877 F 0.4048930.291490 0.637465 −2.600436 11.893505 3.335820 −0.310794 G −0.196701−0.150222 −0.502455 1.981063 −8.639791 −1.725537 0.118939 H 0.0376870.034091 0.155741 −0.570759 2.727763 0.399212 −0.017004 J 0 0 0 0 0 0 0Third Exemplary Embodiment S8 S9 S10 S11 S12 K −17.83478 −64.15173−1.49159 −9.97846 −6.56149 A −0.150081 −0.059463 0.204317 −0.086943−0.138806 B 0.107785 0.013528 −0.287397 −0.063157 0.084164 C −0.071794−0.042805 0.244045 0.097511 −0.042268 D −0.023610 0.059564 −0.125089−0.044942 0.015340 E 0.081621 −0.057366 0.042703 0.010812 −0.003894 F−0.062110 0.029950 −0.009650 −0.001478 0.000659 G 0.021334 −0.0073380.001278 0.000109 −0.000070 H −0.002799 0.000672 −0.000073 −0.0000030.000004 J 0 0 0 0 −0.0000001

Table 7 represents values of Conditional Expressions of the opticalimaging systems in the first example 100, the second example 200, andthe third example 300 described herein. As seen in Table 7, the opticalimaging systems in the first example 100, the second example 200, andthe third example 300 described herein satisfy all of numerical rangesof Conditional Expressions discussed herein.

TABLE 7 Conditional First Second Third Expression Example ExampleExample f1/f2 −0.4385 −0.42956 −0.43280 V5 − V4 32.600 32.600 32.600OAL/FOV 0.0587 0.0621 0.0599 Th6/Th5 0.5776 0.5932 0.5453

As set forth above, in the embodiments disclosed herein, an opticalimaging system appropriate for a small camera module having highperformance may be implemented.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from an object side, wherein at least two of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens include at least one inflection point, and an object-side surface of the sixth lens is concave, wherein the second lens has a refractive index greater than a refractive index of the first lens, a refractive index of the third lens, a refractive index of the fourth lens, a refractive index of the fifth lens, and a refractive index of the sixth lens.
 2. The optical imaging system of claim 1, wherein one of an object-side surface and an image-side surface of the fourth lens includes an inflection point.
 3. The optical imaging system of claim 1, wherein one of an object-side surface or an image-side surface of the fifth lens includes an inflection point.
 4. The optical imaging system of claim 1, wherein one of the object-side surface or an image-side surface of the sixth lens includes an inflection point.
 5. The optical imaging system of claim 1, wherein the fourth lens has a refractive index less than a refractive index of the second lens and greater than a refractive index of the first lens, a refractive index of the third lens, a refractive index of the fifth lens, and a refractive index of the sixth lens.
 6. The optical imaging system of claim 1, wherein the first lens has positive refractive power.
 7. The optical imaging system of claim 1, wherein the sixth lens has negative refractive power.
 8. The optical imaging system of claim 1, wherein an object-side surface of the fifth lens is convex.
 9. The optical imaging system of claim 1, wherein an f-number of the optical imaging system is less than 2.0.
 10. An optical imaging system comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from an object side, wherein one of an image-side surface of the first lens and an image-side surface of the third lens is concave, one of an object-side surface of the fourth lens and an image-side surface of the fourth lens includes an inflection point, one of an object-side surface of the fifth lens and an image-side surface of the fifth lens includes an inflection point, one of an object-side surface of the sixth lens and an image-side surface of the sixth lens includes an inflection point, and V4 is an Abbe number of the fourth lens, V5 is an Abbe number of the fifth lens, and V5-V4 is greater than 20 and less than
 40. 11. The optical imaging system of claim 10, wherein the second lens has a refractive index of 1.65 or higher.
 12. The optical imaging system of claim 10, wherein the fourth lens has a refractive index of 1.6 or higher.
 13. The optical imaging system of claim 10, wherein OAL is a distance from an object-side surface of the first lens to an imaging plane, FOV is a field of view of the optical imaging system, and OAL/FOV is greater than 0.05 and less than 0.2.
 14. The optical imaging system of claim 10, wherein an object-side surface of the fifth lens is convex.
 15. The optical imaging system of claim 10, wherein an object-side surface of the sixth lens is concave. 